Mechanical rectifier



Sept. 10, 1957 F. KOPPELMANN 2,896,196

MECHANICAL RECTIFIER Original Filed Feb. 1, 1950 Ill "fnvemor; f 20/175 AQ/FELMAA/IV Unite; States atent this application May 27, 195;, Seriai No.

Original application February 1, 1950, Seria now Patent No. 2,693,576, dated Nm Divided and 357,781

Claims priority, application Germany Early 16, 1949 6 Claims. (Cl. 321-4) The present application is a division of my U. S. patent application Serial No. 141,638, filed February 1, 1950, entitled Mechanical Rectifier, now Patent No. 2,693,576.

The present invention relates to a mechanical rectifier for use in combination with a D. C. galvanometer.

It is an object of the present invention to provide a mechanical rectifier enabling a direct measurement of the phase angle between a current and the voltage causing the current.

It is another object of the present invention to provide a mechanical rectifier which can be combined with a galvanometer as a single instrument in a casing having standard dimensions.

It is a further object of the present invention to provide a mechanical rectifier with a stationary contact and a movable contact which allows the accurate adjustment of the closing time of the contacts and their phase relation with respect to an alternating electrical quantity such as an A. C. voltage.

The invention comprises in its broadest aspects in combination a contact arrangement including a stationary contact piece and a movable contact piece, means for supplying an alternating electrical quantity to the contact pieces, a synchronous motor adapted to be fed with a current synchronous with the alternating quantity supplied to the contact pieces and driving the movable contact piece so as to periodically make and break the contact between the contact pieces, means for adjusting the portion of the cycle of the alternating quantity during which the contact pieces are making contact with each other, means for adjusting the phase angle between the alternating quantity supplied to the contact pieces and the time at which the contact between said contact pieces is established, and means for rotating the contact arrange-v ment as a whole through an angle of not more than 180".

In a preferred embodiment of the present invention a crank is provided having a pin adapted to move the movable contact piece and a synchronous motor drives the crank, thereby periodically making and breaking the contact between the contact pieces.

in a preferred embodiment of the present invention the synchronous motor comprises a stator and a rotor driving the crank, and means are provided for rotating the stator with respect to the rotor, thereby adjusting the phase angle between the alternating quantity supplied to the contact pieces and the time at which the contact between the contact pieces is established.

Prefera'bly the position of the stationary contact piece is adjustable in order to adjust the portion of the period of the alternating quantity during which the contact pieces are making contact with each other.

In a preferred embodiment of the present invention a stationary contact and a movable contact are arranged in a member which is rigidly connected to a tube-like member enclosing the shaft of the synchronous motor.

A measuring instrument according to the present invention comprises in combination, a casing preferably of the size of a normal precision instrument casing, a moving coil galvanome-ter in the casing preferably having a series resistance and shunt resistance for voltage and current measurements, respectively, and a mechanical rectitier of the type described, the member enclosing the contact arrangement of the rectifier being arranged on the casing of the instrument for rotation through an angle of not more than 180.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a plan view of a measurinx instrument according to the present invention;

Fig. 2 is an enlarged plan view of a detail of the instrument shown in Fig. 1;

Fig. 3 is a vertical section through the parts shown in Fig. 2 and the neighboring parts shown in Fig. 1;

Fig. 4 is a wiring diagram of the instrument shown in Fig. 1; and

Figs. 5 and 6 are diagrams for explaining the operation of the instrument according to the invention.

Referring now to the drawings and first to Figure 1, a casing 16 preferably having the size of a normal precision instrument casing is provided on its top face with a window 12 for a moving coil galvanometer indicated at 112 in Fig. 4 and of which only the scale 14 and the pointer 16 are visible in Fig. 1. Furthermore a mechanical rectifier to be described hereinafter more in detail is arranged partly within and partly outside of the casing 10.

Referring now to Figs. 1 to 3, it will be seen that the mechanical rectifier comprises a stationary contact piece 18 and a movable contact piece 20. The movable contact piece 20 is provided at one end of a leaf spring 22 held with its other end in a bearing number 24. A rubber sleeve 25 encloses the main portion of the leaf spring 22 and serves as a dampening means. The leaf spring 22 preferably consists of a steel band having a thickness of a few tenths of a millimeter and a uniform width of 2 mm. The contact making surfaces of the contact pieces 18, 29 are made from a precious metal such as gold in order to keep the contact resistance as low as possible, for instance in the order of magnitude of V ohm. The bearing member 24 is arranged on a base plate 26 carrying the whole contact arrangement, indicated by 114 in Fig. 4.

The stationary contact piece 18 is carried by an arm 28 pivoted at 3th to the base plate 26 and having an eX- tension 32 which is under the action of a helical spring 34 attached at 36 to the base member 26 and urging the stationary contact piece it; towards the movable contact piece 20. This motion is limited by a conical member 33 against which the bent-04f portion of the extension 32 abuts. The conical member 38 is rigidly connected to a shaft 49 screwed into the rear wall 42 of a hollow member 44 enclosing the contact arrangement 114 and carrying the base plate 25. Shaft 40 is connected to a knob 46 for adjusting the conical member 33 and thereby limiting the distance through which the spring 34 can pull the stationary contact piece 1 3 towards the movable contact piece 20.

Member 44 is provided on its upper wall with a window 48 through which the contact pieces 18 and 20 can be observed. The member 44 is shaped as shown in Figs.

1-3 and arranged for rotation on the casing in a manner to be described hereinafter. The member 44 carries a mark 50 on its tip which cooperates with a scale 52 provided on the top face of the casing 10 and protected by a window 54.

The movable contact piece 20 is acted upon by a crank arrangement including a pin 56 (Fig. 2) which is rigidly connected to a crank disc 58 in an eccentric position. The pin 56 is made from hardened steel and the leaf spring 22 is provided with a silver covering at the spot where it comes into contact with the pin 56. The crank disc 58 is driven by the shaft 60 of a synchronous motor generally indicated by 62 (Fig. 3). During the rotation of the crank disc 58 contact piece 20 is moved out of contact with the stationary contact piece 18 for a portion of a complete rotation of the disc 58 the length of which depends on the position of the stationary contact piece 18 which can be adjusted by turning the knob 46 as described hereabove.

Current conductors 64 and 66 (Fig. 3) lead the current, respectively, to the pivot 30 of. the lever 28 carrying the stationary contact piece 18, and the bearing member 24 carrying the leaf spring 22 which, in turn, carries the movable contact piece 20. The conductors 64 and 66 enter the member 44 from below through a piece of tubing 68 connected to the base plate 26 of the member and moving in a slot 70 of the casing 10 when themember 44 is rotated.

The shaft 60 of the synchronous motor 62 is arranged with its upper end at the center of rotation 72 of the member 44 and the crank disc 58 (Figs. 1 and 3). The member 44 and the contact arrangement 114 can be rotated about the center '72 through an angle of 180 consisting of 90 to either side of the mid position indicated in Fig. 1 by the mark 0. The mark 50 may be provided with a notch cooperating with a rest provided at the position 0. Similar rests may be provided at the positions 90 and +90. The mark 50 in cooperation with the scale 52 allows the direct reading of angular displacement of the member 44. i

The synchronous motor 62 comprises a stator 74 carrying exciting windings 76 to which a single phase current is supplied by conductors 78 and 80 (Fig. 3). The stator '74 of the motor surrounds the rotor 82 connected to the shaft 60. A tube-like member 84, preferably made of brass, fills the air gap between the stator 74 and the rotor 82 and encloses the shaft 60. The tube-like member 84 is at its upper end rigidly connected to the base plate 26 and the member 44. It rests with a flange 86 on the casing 10 which is provided with a bushing 92 and a thrust bearing 94 for the lower end of the shaft 60. The thrust bearing 94 is acted upon by a helical spring 96 the lower end of which abuts against a plate 98 connected to the stopper 90 by screwing or welding. The upper end of the shaft 60 which is connected to the crank disc 58 passes through a bushing 100. The bushings 92 and 168 are preferably made from pure silver whereas the thrust bearing 94 on which the bevelled lower end of the shaft 60 rotates, preferably consists of a precious stone or glass. In this way, the ends of the shaft 60 are supported by the bearings with very low friction and with little play.

The stator 74 of the synchronous motor 62 is provided, preferably on the perimeter of its upper end face, with a toothed rim 102 engaged by a pinion 104 rigidly secured to a shaft 106 adjustable by a knob 108 (Figs. 1 and 3) and rotatably arranged in the casing 10 parallel to the shaft 60. By means of the knob 1138 the stator 74 can be given any angular displacement with respect to the axis of the rotor 82 and the shaft 60.

The synchronous motor 62 should rotate the rotor with a constant angular velocity so that no angular deviations occur in the device according to the invention. The

rotor should be rigidly connected to the crank disc 58 and the pin 56 by means of the shaft 60 so that variations of the driving voltage or the like do not affect the accuracy of the measurement. The exciting field of the motor should be shielded by suitable means (not shown) so that no appreciable voltages are induced in the measuring circuit, these voltages preferably not exceeding 10* volts. The driving voltages should be single phase and the input of the motor as small as possible. If desired a rotary field can be provided by an auxiliary voltage in which the rotor operates either by hysteresis in case it it made of steel or as a synchronous short 'circuited armature provided with a damping winding.

It will be understood that the bearings of the shaft 60 rotate together with the member 44 and that the stator 74 is roatably arranged with respect to the tubular member 84 and rests on a flange 110 thereof.

Referring now to the diagram shown in Fig. 4 it will be seen that the moving coil galvanometer 112 is connected in series with the contact arrangement 114 including the contact pieces 18 and 20. The moving coil galvanometer 112 can be short circuited by a short circuiting member 116 connected to the terminals 118 and 120 whereas the contact arrangement 114 can be short circuited by a short circuiting member 122 connected to the current terminal 120 of the galvanometer 112 and the contact arrangement 114 and the terminal 124.

Normally, the galvanometer 112 and 114 are not short ci'rcuited and the short circuiting member 116 connects the terminal 124 to a terminal 126 and a wire 128 leading to one side of a change over switch 130 connected by a wire 132 to the moving coil galvanometer 112.

Parts 116 to 126 are also shown in Fig. 1. The change over switch 130 connects the wires 128 and 182 to a double pole switch 134 which has four different operating positions of which the third position is shown in Fig. 4. In the first position the switch 134 is connected by means of an adjustable series resistance 136 arranged in the casing 10 (see Fig. 1) to a pair of terminals 138, 140

In the fourth position the switch 134 connects the galvanometer to a battery 152 and an adjustable series resistance 154. These serve for controlling the time of contact engagement of contact pieces 18 and 20 and are used by short circuiting the contact arrangement 114 by the short circuiting member 122 and adjusting resistance 154 so that the galvanometer 112 shows a full defiec 'tion of its pointer 16. Then the short circuiting member 122 is removed so that the deflection of the galvanometer is reduced to a fraction of a full deflection corresponding to the fraction of a full cycle which the closing time of the contact arrangement 114 occupies.

Fig. 4 shows also the winding 76 of the synchronous motor 62 with its conductors 78 and 80 to which a current is applied, which is synchronous with the quantity to be measured. If the instrument is to be used without the 'moving coil galvanometer in connection with an external galvanometer, for instance of the mirror type, the short circuiting member 116 is transferred from the position shown in full lines in Fig. 4 to the position shown in dotted lines in which it short circuits the moving coil galvanometer 112.

The operation of the device will now be explained in connection with the moving coil galvanometer 112. The

to the mid position marked on the scale 52. In this position the pointer 16 of the galvanometer 112 deflects to the right or to the left from its mid position according to the phase difference of the voltage with respect to the synchronous voltage driving the motor. By means of the knob 108 the stator 74 of the synchronous motor 62 is rotated so that the pointer 16 moves once more into its mid position. The position of the phase of the voltage to be measured with respect to the closing and opening time of the contact arrangement which must be satisfied in this condition is shown in Fig. in which the curve in represents the quantity to be measured, in this case, the voltage applied to the terminals 133 and 140. The voltage has its crest of the negative half wave coinciding with the closing time C of the contact arrangement 114 and the crest of the positive half wave coinciding with the opening time 0 of the contact arrangement. Now the contact arrangement 114 is rotated through 90 by rotating the member 44 to the position in which the mark coincides with on the dial 52. This rotation causes a relative position of the curve in with respect to the closing and opening times C and O of the contact arrangement shown in Fig. 6, where the positive half wave of the curve m coincides with the time between C and 0. Therefore the galvanometer 112 will now show a deflection corresponding to half the arithmetical mean value of the positive half wave of the curve m.

In a similar way the instrument may be used for a current measurement, the switch 134 being brought into its third position connecting the galvanometer 112 and the contact arrangement 114 to terminals 146 and 148.

The instrument may also be used for directly indicating the phase angle between a current and a voltage. In order to accomplish this, switch 134 is first brought into the first position connecting terminals 138 and 140 to the galvanometer 112 and the contact arrangement 114, and the stator 74 is rotated by the knob 108 into a position in which the pointer 16 of the galvanometer 112 shows no deflection while the member 44 is in its mid position. Then the switch 134 is switched into the third position in which it connects the current terminals 146 and 143 to the galvanometer 112 and the contact arrangement lid. The pointer 16 of the galvanometer 112 will now show a deflection which is made to disappear by a rotation of the member 44 without actuating the knob 1&8. The phase angle may then be read from the position of the mark 59 on the scale 52. This phase difference is leading if member i -l has to be rotated to the right and lagging if it has to be rotated to the left.

it should be understood that by means of the knob 46 the contact time of the contact arrangement can be adjusted to any value up to or a half cycle, and this adjustment can be checked by bringing the switch 134 into its fourth position where it is connected to the battery 152 and the series resistance 154. This check can be made at any time even during a series of correlated measurements in order to compensate any change of the contacting time due to mechanical or electrical loads which could lead to errors in measurement.

The purpose of the change over switch 136 is to change the sign of the deflections of pointer 16 without rotating member 44. and the contact arrangement 11d. For instance, if the deflection of the pointer 16 is negative it can be made positive by simply switching over the change over switch 130.

With the instrument described hereinabove voltages and currents can be measured which have very small values. Furthermore phase angles may be directly measured. Resistive and reactive components of currents may also be measured as will be evident to anyone skilled in the art. Further it is possible by means of inductive or capacitative series and shunt resistances to obtain a record of the time curve of the quantity to be measured. If the quantity to be measured is not a simple sine wave,

7 6 the fundamental wave and the harmonics can be ascertained.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of mechanical rectifiers differing from the types described above.

While I have illustrated and described the invention as embodied in a mechanical rectifier for use in connection with a moving coil galvanometer, I do not intend to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of my invention.

Without further analysis, the foregoing will so fully reveal the gist of my invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of he generic or specific aspects of this invention and, Lerefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What I claim as new and desire to secure by Letters Patent is:

l. A mechanical rectifier for alternating current measuring instruments, comprising, in combination, a plate; a contact arrangement arranged on said plate and including a stationary contact piece and a movable contact piece cooperating therewith; a bearing member arranged on said plate; a leaf spring carrying at one end thereof said movable contact piece, the other end of said leaf spring being held in said bearing member; a crank arrangement acting on said leaf spring; means for supplying an alternating current to said contact pieces; a synchronous motor having a stator and a rotor; a shaft connected to said rotor and driving said crank arrangement acting on said leaf spring carrying said movable contact piece so as to periodically make and break the contact between said contact pieces; means for feeding said stator with a current synchronous with the alternating current supplied to said contact piece; means for rotating said stator with respect to said rotor, thereby sting the phase angle between the alternating current lied to said contact pieces and the time at which the contact between said contact pieces is established; an arm having two ends, one of said two ends being pivoted to said plate, the other of said two ends being curved, said stationary contact piece being rigidly conted to an intermediate point of said arm; and means or adjusting said curved end of said arm so as to adjust to any portion of the period of the alternating current the time period during which said contact pieces are making contact with each other.

2. A mechanical rectifier for alternating current measuring instruments, comprising, in combination, a casing; a hollow member arranged on said casing for rotation through an angle of 90 to either side; a base plate carried by said hollow member; a contact arrangement on said base plate and including a stationary contact piece and a movable contact piece cooperating therewith; a bearing member arran ed on aid base plate; a leaf spring carrying at one end thereof said movable contact piece, the other end of said leaf spring being held in said bearing member; a crank arrangement acting on said leaf spring; means for supplying an alternating current to said contact pieces; a synchronous motor having a stator and a rotor; a shaft connected to said rotor and driving said crank arrangement acting on said leaf spring carrying said movable contact piece so as to periodically make and break the contact between said contact pieces; means for feeding said stator with a current synchronous with the alternating current supplied to said contact pieces; means for rotating said stator with respect to said rotor, thereby adjusting the phase angle between the alternating current supplied to said contact pieces and the time at which the contact between -'-7 said contact pieces is established; an arm having two ends, one of said two ends being pivoted to said plate, the

other of said two ends being curved, said stationary contact piece being rigidly connected to an intermediate point of said arm; and means for adjusting said curved end of said arm so as to'adjust to any portion of the period of the alternating current the time period during which said contact pieces are making contact with each other.

3. A mechanical rectifier for alternating current measuring instruments, comprising, in combination, a casing; a hollow member arranged on said casing for rotation through an angle of 90 to either side; a base plate carried by said hollow member; a contact arrangement arranged on said base plate and including a stationary contact piece and a movable contact piece cooperating therewith; a bearing member arranged on said base plate; a leaf spring carrying at one end thereof said movable contact piece, the other end of said leaf spring being held in said bearing member; a crank arrangement acting on said leaf spring; means for supplying an alternating current to said contact pieces; a synchronous motor having a stator and a rotor; a shaft connected to said rotor and driving said crank arrangement acting on said leaf spring carrying said movable contact piece so as to periodically make and break the contact between .said contact pieces; means for feeding said stator with a current synchronous with the alternating current supplied to said contact pieces; means for rotating said stator with respect to said rotor, thereby adjusting the phase angle between the alternating current supplied to said contact pieces and the time at which the contact between said contact pieces is established; an arm having two ends, one of said two ends being pivoted to said plate, the other of said two ends being curved, said stationary contact piece being rigidly connected to an intermediate point of said arm; a conical member arranged rotatably about the axis thereof and longitudinally displaceable along said axis, said conical member having a curved face engaging said curved end of said arm; resilient means attached to said arm and urging said curved end thereof into engagement with said curved face of said conical member; and manually operated means for rotating said conical member and simultaneously displacing the same along the axis thereof so as to adjust to any portion of the period of the alternating current the time period during which said contact pieces are making contact with each other.

4. A mechanical rectifier for alternating current measuring instruments, comprising, in combination, a plate; a contact arrangement arranged on said plate and including a stationary contact piece and a movable contact piece cooperating therewith; a bearing member arranged on said plate; a leaf spring carrying at one end thereof said movable contact piece, the other end of said leaf spring being held in said bearing member; a rubber sleeve enclosing the main portion of said leaf spring and dampening the oscillations thereof; a crank arrangement acting on said leaf spring; means for supplying an alternating current to said contact pieces; a synchronous motor having a stator and a rotor; a shaft connected to said rotor and driving said crank arrangement acting on said leaf spring carrying said movable contact piece so as to periodically make and break the contact between said contact pieces; means for feeding said stator with a current synchronous with the alternating current supplied to said contact pieces; means for rotating said stator with respect to said rotor, thereby adjusting the phase angle between the alternating current supplied to said contact pieces and the time at which the contact between said contact pieces is established; an arm having two ends, one of said two ends being pivoted to said plate, the other of said two ends being curved, said stationary contact piece being rigidly connected to an intermediate point of said arm; and means for adjusting said curved end of said arm so as to adjust to any portion of the iii) period of the alternating current the time period during which said contact pieces are making contact with each other. 7

5. A mechanical rectifier for alternating current measuring instruments, comprising, in combination, a casing; a hollow member arranged on said casing for rotation through an angle of 90 to either side; a base plate carried by said hollow member; a contact arrangement arranged on said base plate and including a stationary contact piece and a movable contact piece cooperating therewith; a bearing member arranged on said base plate; a leaf spring carrying at one end thereof said movable contact piece, the other end of said leaf spring being held in said bearing member; a rubber sleeve enclosing the main portion of said leaf spring and dampening the oscillations thereof; a crank arrangement acting on said leaf spring; means for supplying an alternating current to said contact pieces; a synchronous motor having a stator and a rotor; a shaft connected to said rotor and driving said crank arrangement acting on said leaf spring carrying said movable contact piece so as to periodically make and break the contact between said contact pieces; means for feeding said stator with a current synchronous with the alternating current supplied to said contact pieces; means for rotating said stator with respect to said rotor, thereby adjusting the phase angle between the alternating current supplied to said contact pieces and the time at which the contact between said contact pieces is established; an arm having two ends, one of said two ends being pivoted to said plate, the other of said two ends being curved, said stationary contact piece being rigidly connected to an intermediate point of said arm; and

.means for adjusting said curved end of said arm so as to adjust to any portion of the period of the alternating current the time period during which said contact pieces are making contact with each other.

6. A mechanical rectifier for alternating current measuring instruments, comprising, in combination, a casing; a hollow member arranged on said casing for rotation through an angle of 90 to either side; a base plate carried by said hollow member; a contact arrangement arranged on said base plate and including a stationary contact piece and a movable contact piece cooperating there with; a bearing member arranged on said base plate; a leaf spring carrying at one end there of said movable contact piece, the other end of said leaf spring being held in said bearing member; a rubber sleeve enclosing the main portion of said leaf spring and dampening the oscillations thereof; a crank arrangement acting on said leaf spring; means for supplying an alternating current to said contact pieces; a synchronous motor having a stator and a rotor; a shaft connected to said rotor and driving said crank arrangement acting on said leaf spring carrying said movable contact piece so as to periodically make and break the contact between said contact pieces; means for feeding said stator with a current synchronous with the alternating current supplied to said contact pieces; means for rotating said stator with respect to said rotor thereby adjusting the phase angle between the alternating current supplied to said contact pieces and the time at which the contact between said contact pieces is established; an arm having two ends, one of said two ends being pivoted to said plate, the other of said two ends being curved, said stationary contact piece being rigidly connected to an intermediate point of said arm; a conical member arranged rotatably about the axis thereof and longitudinally displaceably along said axis, said conical member having a curved face engaging said curved end of said arm; resilient means attached to said arm and urging said curved end thereof into engagement with said curved face of said conical member; and manually operated means for rotating said conical member and simultaneously displacing the same along the axis thereof so as to adjust to any portion of the period of the alternat- 9 ing current the time period during which said contact 2,227,937 pieces are making contact with each other. 2, 37 5,4 1

References Cited in the file of this patent UNITED STATES PATENTS 5 1,281,673 Seeley Oct. 15, 1918 10 Koppelmann Jan. 7, 1941 Huber May 8, 1945 FOREIGN PATENTS Germany Nov. 26. 1923 Germany Oct. 2, 1952 

